This application claims priority of French patent application 0107782, filed Jun. 14, 2001.
This invention concerns the field of smart cards and more specifically a contactless smart card having an adapter made of paper.
The smart card sector is undergoing full expansion. These tools, which have become widespread in the form of bank cards and telephone cards, have witnessed a considerable second growth with the development of new technologies and notably the advent of contactless technology. New applications have indeed been invented. For example, in the transportation sector, the contactless smart card was developed as a means of payment for both mass transit and highway systems. The electronic wallet represents yet another application for contactless smart cards as a means of payment. Many companies have also developed identification means for their personnel using contactless smart cards.
The exchange of information between the contactless card and the associated reader is accomplished by remote electromagnetic coupling between an antenna lodged in the contactless card and a second antenna located in the reader. For developing, storing and processing the information, the card is equipped with a contactless chip or electronic module which is connected to the antenna. The antenna and the chip or contactless module are typically located on a dielectric support made of plastic material (polyvinyl chloride (PVC), polyester (PET), polycarbonate (PC) . . . ). The antenna is obtained by chemical copper or aluminum etching on the support or winding of conductive metal wire such as copper.
The card is often monobloc. The antenna support is inserted between two layers of plastic materials (PVC, PET, PC, acrylonitrile-butadiene-styrene (ABS) . . . ) forming the upper and lower card bodies and then heat bonded by hot lamination under pressure. The contactless chip or module is connected to the antenna by an electrically conductive glue or equivalent which enables the ohmic contact to be established.
However, a card of this type has several major drawbacks. The most significant drawback is that the plastic heat bonding operation, implemented during the lamination process, leads to a monobloc card having mediocre mechanical properties in terms of the restitution of absorbed stresses. When the card is subjected to excessive bending and/or twisting stresses, all of the stress applied is transmitted to the contactless chip or electronic module and primarily to the bonding points which make the connections. The mechanical strength of the bonding joints is subjected to great strain which can cause the chip-antenna or contactless module-antenna connection to break. The antenna may also be cut as a result of these mechanical stresses.
Another drawback of traditional contactless smart cards is their cost price. Using an antenna obtained through chemical etching or by coiling metal wire is responsible for a high cost price which is not very compatible with widespread distribution of this type of tool. Furthermore, the use of a contactless electronic module increases this cost price.
In order to counter these drawbacks, another manufacturing process, described in French patent No. 9915019, consists in using a fibrous support such as paper on which the antenna is screen printed using conductive ink. The antenna support is then subjected to a heat treatment to cure the ink. The following steps consist in connecting the chip and the antenna and soldering the card bodies onto the antenna support from both sides by hot press molding, this last step being the lamination step.
The drawback encountered with this method resides in the fact that the rigidity of the chip on which the contacts are glued on the antenna contacts to establish the connection, leads to cracks which form in the conductive ink comprising the antenna during the lamination step. As a result, the connection between the chip and the antenna is sometimes cut, in all cases made fragile, and may break at any time and particularly when external stresses are encountered.
The first object of the invention is thus to mitigate these drawbacks by supplying a contactless smart card which resists the mechanical stresses associated with its use and whose cost price is low owing to the use of inexpensive materials.
A second object of the invention is to supply a contactless smart card whose connections between the antenna and the chip are not fragilized during the card""s lamination step.
The invention thus concerns a contactless smart card featuring an antenna on an antenna support made of fibrous material, the antenna consisting of at least one turn of conductive ink and two contacts which are screen printed on the antenna support, each of the card bodies being made up of at least one layer of plastic material, and a chip, provided with contacts connected to the antenna. This card also includes a chip support made of fibrous material featuring two strips of polymerizable conductive ink, screen printed on the chip support, on which are connected the chip""s contacts, the chip support being positioned on the antenna support so that the polymerizable conductive ink strips come into contact with the antenna""s contacts and connect with them, and so that the chip is positioned in a cavity in the antenna support created for this purpose so that no rigid element of the chip is in contact with the antenna""s contacts or the antenna itself. Another purpose of this invention is a smart card manufacturing process, including the steps of:
manufacturing an antenna consisting in screen printing turns printed using polymerizable conductive ink and two contacts for the antenna on an antenna support made of fibrous material and to subject this antenna support to heat treatment so as to bake and polymerize the conductive ink,
creating a cavity in the antenna support by a cutout in the latter,
manufacturing a chip support made of fibrous material by screen printing two strips of polymerizable conductive ink on a support made of fibrous material,
connecting a chip, featuring contacts on the chip support, so that the chip""s contacts are in contact with the strips of polymerizable conductive ink,
positioning the chip support on the antenna support so that the strips of polymerizable conductive ink are in contact with the contacts of the antenna and so that the chip is located in the cavity, and
laminating the card body on each side of the antenna support, consisting in welding at least one layer of plastic material to each side of the support by means of hot press molding.